You just include both of them in the search box. However, I tried it with your words and it says that WBM is "either very common, too long, or too short and were not included in your search." However, if I use a word at least four characters long, it seems to work. I'm guessing they have a minimum word size in order to optimize the searches cuz if they had to index all words that are three letters or less it would add a lot of work and time to the searches.